Wireless access is not really the problem. You have this problem for all users on your network. For computers in your local space that are hardwired, you can set them up for automatic updating, or run around and update them all manually when you need to. It is difficult to run around and apply updates to remote users whether they use wireless, dial-up or Internet connection.
What you need is a desktop management system, such as Microsoft's SMS or CA's Unicenter. As noted in other answers, mention of a product name does not imply endorsement. There are many such products in this line of software and you should do your own evaluation to determine which is best for your own application.
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This was first published in February 2004